The present invention relates to a magnetic head for magnetic recording, a head gimbal assembly, and a magnetic recording and reproducing apparatus, and more specifically to a microwave-assisted magnetic head and a line configuration of a microwave magnetic field generating element.
It is desired to increase a recording density of a magnetic recording medium device, which is a magnetic recording device. In order to achieve a signal quality (an S/N ratio) necessary for high-density recording, as a areal recording density increases, it is necessary to make magnetic particles be smaller that constitute a magnetic recording medium. However, magnetic particles that have been made smaller tend to lose magnetization because of thermal fluctuations. In order to prevent this and keep a stable recording state, it is necessary to increase magnetic anisotropy energy Ku of magnetic particles. For magnetic particles having uniaxial magnetic anisotropy, the strength of a magnetic field necessary to make magnetization reversal is called an anisotropic magnetic field (Hk), which is expressed using saturation magnetization (Ms) and magnetic anisotropy energy (Ku) as Hk=2Ku/Ms. Thus, in the case where a material having a high Ku is used, Hk is increased and a higher recording magnetic field is necessary to perform recording on a magnetic recording medium. In contrast, as a areal recording density is increased, the size of a recording head element is reduced. Thus, the strength of a magnetic field that may be generated decreases proportionately with the size of a recording head. As a result, recording to be performed on the magnetic recording medium becomes difficult.
To perform magnetization reversal of a recording film in accordance with desired data series, a write head element of a thin film magnetic head needs to apply an abrupt recording magnetic field having, at maximum, an strength of the order of the anisotropic magnetic field (Hk) of the recording film. In a magnetic disk drive (HDD) that has become commercially practical using a perpendicular magnetic recording method, a write head element using a so-called monopole is used and a recording magnetic field is applied to a recording film in a perpendicular direction from a surface of an air bearing surface (ABS) of the recording head element. The strength of this perpendicular recording magnetic field is proportional to a saturation magnetic flux density (Bs) of a soft magnetic material that constitutes the monopole, and thus a material having a saturation magnetic flux density (Bs) that is made as high as possible has been developed and has become commercially practical. However, as a saturation magnetic flux density (Bs), Bs=2.4 T (tesla) is practically the upper limit from a so-called Slater-Pauling curve, and a value obtained under present circumstances is approaching the practical limit. In addition, the thickness and width of a monopole currently used is on the order of about 100 nm to 200 nm; however, in the case where a recording density is increased, it is necessary to further reduce the thickness and width. As a result, a perpendicular magnetic field to be generated is further reduced.
In this manner, under present circumstances, it is becoming more difficult to achieve higher density recording because of the limit of the recording capability of a write head element. In order to solve this technical problem, energy assisted recording has been proposed in which, when recording is performed, energy is applied to a magnetic recording medium in an auxiliary manner and a recording magnetic field strength is reduced.